Bitumen production from thermal EOR operations continues to increase with time, with the use of solvent co-injection with steam to increase oil rates and reduce steam-oil ratios for SAGD (Steam Assisted Gravity Drainage) and CSS (Cyclic Steam Stimulation) operations. Encouraging results from several field tests suggest that this enhancement to the steam-only operations will one day become commonplace.
Operators may experience asphaltene deposition in co-injection operations where light hydrocarbon solvents are used (e.g. propane, butane, pentane, etc.). Use of these light hydrocarbons within the reservoir may cause asphaltene molecules to separate from heavy oils, which is advantageous to selectively increase the amount of higher API oil produced from the reservoir while delaying or preventing the production of undesired asphaltenes on the surface. Field trials using propane and butane for in situ deasphalting to increase the API gravity during heavy oil production have been reported.
There is a need for an improved method to address the effect of asphaltenic materials in the production of heavy oil with the use of volatile solvents.